In 27 patients (mean age at death 72 plus/minus 9 years) with abdominal aortic aneurysm (AAA) greater than or equal to 5.0 cm in its widest transverse diameter, the amounts of narrowing at necropsy in the 4 major (left main, left anterior descending, left circumflex, and right) epicardial coronary arteries were determined. During life, 12 (44%) of the 27 patients had symptoms of myocardial ischemia: angina pectoris alone in 2, acute myocardial infarction alone in 3, angina pectoris and acute myocardial infarction in 5, and sudden coronary death in 2. Ten (37%) of the 27 patients died from consequences of myocardial ischemia. Six (22%) died from rupture of the AAA. Grossly-visible left ventricular necrosis and/or fibrosis was present in 15 (56%) patients. Of the 27 patients, 23 (85%) had narrowing 76-100% in cross-sectional area of 1 or more major coronary arteries by atherosclerotic plaque. The mean number of coronary arteries per patient severely (greater than 75%) narrowed was 2.0 plus/minus 1.3/4.0. Of the 108 major coronary arteries in the 27 patients, 55 (51%) were narrowed greater than 75% in cross-sectional area by plaque. The 4 major coronary arteries in the 27 patients were divided into 5-mm segments and a histologic section, stained by the Movat method, was prepared from each segment. The mean percents of the resulting 1,475 five-mm segments narrowed in cross- sectional area 0-25%, 26-50%, 76-90%, and 96-100% were 17, 37, 28, 15, and 3%, respectively. The percents of 5-mm coronary segments narrowed greater than 75% in cross-sectional area were similar in the right, left anterior descending, and left circumflex coronary arteries. Thus, patients with AAA nearly always have diffuse and severe coronary atherosclerosis.